Pervasive Developmental Disorders (PDD)


Also called: PDD


Pervasive developmental disorders (PDDs) are neurological disorders that affect a person’s ability to interact socially and communicate with others. Typical signs include self-isolation, refusal to make eye contact or respond to others, and repetitive movement (e.g., arm-flapping, rocking, head-banging). Mental retardation and cognitive impairment may also occur.

PDDs are usually identified during childhood and symptoms last a lifetime. Children with a PDD may require supervised care for the rest of their lives, depending on the severity of their disorder.

There are five types of PDDs, including autism, Asperger’s syndrome, pervasive developmental disorder not otherwise specified (sometimes called atypical autism), Rett syndrome and childhood disintegrative disorder. The first three are considered autistic spectrum disorders, although this term has been used to describe all PDDs.

Most causes of PDDs are unknown. Genetics and other factors that affect brain chemistry and development are believed to be involved. For example, a specific gene mutation has been identified in 80 percent of patients with Rett syndrome. Vaccines, parenting style and emotional trauma do not cause PDDs.

If parents suspect their child is not meeting age-appropriate developmental milestones, or the child has lost previously acquired social, language or motor skills, they should consult their child’s pediatrician.

Diagnosing PDDs can be a lengthy process because it may involve specialists (e.g., developmental pediatricians, pediatric neurologists, psychologists, speech therapists) and numerous examinations (e.g., physical examination, neurological

examination). Blood tests and hearing tests may also be performed. In general, however, there is no test that identifies the presence of a PDD – diagnosis is made based on symptoms. Parents should be prepared to provide a thorough list of all their child’s symptoms and when they began.

Although PDDs cannot be cured, parents should work with their child’s pediatrician or team of specialists to develop a treatment plan that may help reduce the child’s symptoms. Early intervention may dramatically reduce social problems faced by these children. Treatment may include behavior therapy, medication, and speech, physical and/or occupational therapy.

Caring for children with PDDs can be an extremely frustrating and stressful experience. There are numerous methods to help parents cope with their child’s PDD, including joining a support group, attending family counseling and applying for financial aid to help lessen the financial burden of long-term care for a child with a PDD.

About pervasive developmental disorders

Pervasive developmental disorders (PDDs) are complex neurological disorders that affect a person’s ability to interact socially and communicate with others. These disorders begin in childhood and last a lifetime. They result in impaired social skills (e.g., difficulty interacting with peers), language (e.g., lack of speech or unresponsiveness) and behavior (e.g., repetitive habits).

There are five PDDs. Three of them are also called autistic spectrum disorders:autism, Asperger’s syndrome and pervasive developmental disorder not otherwise specified (also known as atypical autism). The two other disorders are Rett syndrome and childhood disintegrative disorder,which are much less common than the autistic spectrum disorders. The latter two are defined by periods of normal development followed by the loss of previously acquired social, language and motor skills. In common usage, many people refer to all five PDDs as autistic spectrum disorders. 

Children with PDDs do not follow the typical basic development patterns. For example, most babies babble and point by the age of 12 months, use single words by 16 months of age, and develop two-word phrases on their own by the time they are 2 years old. Children with PDDs do not – or they lose the ability to do so shortly after learning such skills.

Cognitive impairment, including mental retardation, may also occur in children with PDDs. Some forms of PDDs are more likely than others to include cognitive deficits. For example, it is estimated that seven in 10 autistic children are mentally retarded, according to the National Mental Health Association.

Most PDDs are also associated with other conditions. These include tuberous sclerosis complex (genetic condition that can cause mental retardation and the growth of benign tumors in the body), fragile X syndrome (genetic condition that causes mental impairment) and seizure disorders such as epilepsy.

Mental illnesses may also occur in children with PDDs, although sometimes not until a child becomes older and recognizes that they are different from others. These disorders may include depression, anxiety disorders, attention deficit hyperactivity disorder (ADHD), and obsessive-compulsive disorder.

According to the Centers for Disease Control and Prevention (CDC), about two to six out of every 1,000 people have PDDs. However, the estimated number of people with PDDs varies greatly. This variance may be attributed to factors such as different diagnostic criteria.The number of reported cases of PDDs has increased in the past 20 years. This increase may be related to heightened public awareness and improved diagnostic capabilities – not necessarily a rise in the number of cases.

Types and differences of PDDs

There are five different types of pervasive developmental disorders (PDDs). Each is a neurological condition occurring during childhood that involves problems with communication, social interaction and behavior. They differ from one another based on the type, severity and onset of their symptoms. The first three listed below are considered autistic spectrum disorders, although this term has been used to describe all five disorders.

The five PDDs are:

  • Autistic disorder (commonly known as autism). Signs usually appear by the age of 3 years, but are sometimes apparent at 18 months. Children with autism have limited social interactions with others (e.g., avoiding eye contact) and may have limited communication skills. Repetitive rituals and movements, as well as hypersensitivity to light and sound are common. Some behavior may be aggressive and violent (e.g., head-banging, temper tantrums). Mental retardation or some type of cognitive impairment frequently occurs in children with autism. It affects more males than females. Autism is the best known PDD and is one of the more common disabilities that requires the services of special education in the United States, according to the Centers for Disease Control and Prevention (CDC).

  • Pervasive developmental disorder not otherwise specified (PDD-NOS). Sometimes referred to as atypical autism, PDD-NOS involves some, but not all, of the signs required for diagnosis of autism. Children with PDD-NOS usually display significant behavioral impairment. Symptoms may appear later than in cases of autism.

  • Asperger’s disorder (also known as Asperger’s syndrome). Believed to be a mild form of autism that does not typically involve language or cognitive impairment. Children with Asperger’s disorder usually have average to above average intelligence as well as verbal skills. Mental retardation does not typically occur. Children with Asperger’s disorder commonly display impaired social skills and awkward, uncoordinated or clumsy movement. They may be seen as odd or eccentric, but are generally able to function well in society. They may become obsessive about unusual topics (e.g., aliens, bus schedules). Symptoms usually appear between the ages of 2 and 6 years, although the disorder may not be diagnosed until much later. It affects more males than females.

  • Rett syndrome (also known as Rett’s disorder). A rare syndrome, believed to affect one in every 10,000 to 15,000 people, according to the National Institutes of Health (NIH). This disorder involves a period of normal development during infancy, followed by the loss of previously acquired skills (e.g., expressive language, hand use). Signs usually appear between 6 and 18 months of age and include repetitive hand-wringing, inability to control the feet, a decrease in head circumference, walking on toes, seizures, breathing problems, sleep disturbances and gastrointestinal complaints. Rett’s disorder is also associated with mental retardation. It almost exclusively affects females and is sometimes misdiagnosed as autism or cerebral palsy.

  • Childhood disintegrative disorder (CDD). This extremely rare disorder is estimated to affect less than two out of every 100,000 people, according to the NIH. Children with CDD develop normally for the first two years of life, then begin to lose previously acquired language, motor and/or social skills. This usually occurs between the ages of 2 and 4 years – but may occur up to age 10. CDD commonly involves the loss of bowel or bladder control, seizures and low intelligence quotient (IQ). It affects more males than females.

Risk factors and potential causes of PDDs

Pervasive developmental disorders (PDDs) result from abnormalities in the way the brain functions. Research into PDDs, especially autism, has shown abnormalities in several parts of the brain and in a number of different genes. But for most of these disorders, the exact causes are unknown.

Genetics, exposure to toxins or substances that can cause birth defects and prenatal infections (e.g., rubella, cytomegalovirus) are believed to play a role in the development of PDDs. Some studies indicate that food allergies or excessive yeast in the digestive tract may be involved.

The rise in PDD cases in recent years has led to increased research into potential environmental causes, especially the possible involvement of childhood immunizations. Children receive numerous immunizations in their first three years of life, many of which are around the time the initial symptoms of PDDs appear. However, according to the Centers for Disease Control and Prevention(CDC), there is no scientific evidence connecting any vaccine to the onset of PDD. In addition, increased rates of PDD are most likely due to increased public awareness about the disorders and better diagnostic methods – not the use of any particular vaccine.

PDD is not caused by emotional trauma, a psychological disorder, or parenting behavior (e.g., an emotionally detached parent). 

The cause of most cases of Rett syndrome has been identified. A gene mutation on the X chromosome has been detected in 80 percent of girls with the condition.

With the lack of specific causes for most forms of PDDs, there are few identifiable risk factors for the disorders. However, the known risk factors include:

  • Gender. For all PDDs other than Rett syndrome, there are far more boys with the disorder than girls. Scientists speculate that the presence of the Rett gene mutation on the X chromosome means that boys with the mutation were either miscarried during pregnancy or died in their first year, before the Rett symptoms usually appear.
  • Sibling involvement. Families that have one child with a PDD have a greater likelihood of having another child with a PDD.
  • Other developmental disorders. Autism specifically occurs more with other developmental disorders such as mental retardation and fragile X syndrome. In addition, children with autism are more likely to have another family member with some type of communication or language disorder.

Signs and symptoms of PDDs

Signs of pervasive developmental disorders (PDDs) may first appear when a child is 18 months old or even earlier. After a child is diagnosed, parents may recall earlier infant behavior that they identified as different. PDDs may become obvious between the ages of 2 and 6 years – and are usually identified by the age of 3.

Signs and symptoms of PDDs can vary greatly from person to person. For example, two children diagnosed with the same type of disorder (e.g., autism) may display entirely different combinations of symptoms, which can range from mild to severe. No two children with PDDs will have exactly the same symptoms.

Although the types of symptoms and their severity may differ, they should remain constant in all settings. Children with PDDs are consistent in their unusual behaviors – the signs of PDD do not typically change over time or in different environments. Thus, a child who is withdrawn and avoids physical or social contact with classmates at school, but who is attentive and affectionate at home, is not exhibiting signs of a PDD. In addition, some signs (e.g., delayed speech) may indicate many other conditions besides a PDD.

Signs may vary within specific disorders. For example, children with Asperger’s syndrome may have advanced vocabulary and language skills for their age, but may not understand the nuance of the language.

Signs of PDDs may include any combination of the following:

  • Impaired social interaction
    • Difficulty making friends
    • Prefers to be alone; not interested in others
    • Self-absorbed
    • Inability to understand feelings of others or talk about one’s own feelings
    • Hyperactive and inattentive
    • Aggressive behavior (towards self or others)
    • Temper tantrums
    • Dislike of physical contact (e.g., touching, cuddling)
  • Impaired verbal and nonverbal communication
    • Avoids eye contact
    • Does not respond when being spoken to
    • Does not respond to facial expressions
    • Lack of facial expression (e.g., does not smile)
    • Monotone speech (or speaks with an unusual pace or pattern)
    • Limited or no speech
    • Echolalia (involuntary repetition of words others have spoken)
    • Does not point to items or look at an item when another person points to it
    • Misuse or no use of personal pronouns (uses third person or confuses “I” and “you”)
    • Inability to understand nuances of language
  • Repetitive or unusual behaviors/interests
    • Repetitive movements (e.g., hand-wringing, arm flapping, rocking, head-banging)
    • Walking on toes
    • Unusual play (e.g., repetitively shakes, spins or aligns toys/objects)
    • Focuses on one thing for unusually long time (e.g., plays with the same toy over and over)
    • Lack of imagination
    • Lack of curiosity in environment
    • Difficulty with changes in routine or environment (e.g., temper tantrums)

Signs of cognitive impairment, including mental retardation, may appear in children with autism, but do not necessarily occur with all types of PDDs.

Parents are typically the first to notice unusual behaviors in their child. This includes children who fail to meet age-appropriate developmental milestones, or who suddenly lose previously acquired skills (e.g., a babbling, responsive infant who suddenly becomes withdrawn and silent). Parents should consult their child’s pediatrician in the following instances:

  • Child fails to meet normal development milestones, for example:
    • 12 months: babbling, gesturing (e.g., pointing, waving goodbye)
    • 16 months: single words
    • 24 months: two-word spontaneous phrases (not echoing)
  • Child loses previously acquired skills (e.g., language, social, motor skills)

If a pediatrician dismisses these concerns, or advocates waiting to see if a child “grows out of it,” parents are advised to get a second opinion or to visit a specialist (e.g., a developmental pediatrician or pediatric neurologist). Early diagnosis and intervention in cases of PDDs may drastically reduce the severity of a child’s symptoms and increase their future quality of life.

Diagnosis methods for PDDs

Diagnosing pervasive developmental disorders (PDDs) may be difficult. There are no physical or laboratory tests that conclusively identify the presence of a PDD. Thus, diagnosis is generally made on the basis of signs and symptoms. Even then, it is often difficult to distinguish among the various types of PDDs.

For parents concerned about PDDs, diagnosis begins with a visit to their child’s pediatrician. A physical examination may be conducted and a complete medical history compiled. It is important that parents thoroughly describe their child’s symptoms and when each began.

If a PDD is suspected, screening tests, such as the autism spectrum screening questionnaire, may be performed. Depending on test results, further evaluation may be indicated and additional specialists may become involved (e.g., developmental pediatrician, pediatric neurologist, psychologist or psychiatrist, speech pathologist, social worker). Additional tests may include a neurological examination, genetic assessment (to identify abnormalities in a child’s chromosomes), as well as speech, language and psychological testing.

Blood tests may also be conducted, usually to rule out lead poisoning. Children with PDDs may have elevated lead levels in their blood, according to the National Institutes of Health(NIH). Hearing tests are generally performed to rule out hearing loss as the reason for a decline in a child’s responsiveness.

PDDs may be diagnosed based on criteria developed by the American Psychiatric Association.


  • Patient has an abnormal level of function in one or more of the following areas before the age of 3: social interaction, language used in social communication and symbolic or imaginative play.
  • A total of six or more criteria are present from the following three categories:
    • Category one – qualitative impairment in social interaction indicated by at least two of the following:
      • Marked impairment in nonverbal behaviors that are used in social interaction. These include eye contact, facial expressions, body postures and other gestures.
      • Lack of peer relationships appropriate for the patient’s developmental level.
      • Lack of apparent desire to have fun with others, or to seek common interests with others.
      • Lack of “give and take” in social or emotional interactions.
    • Category two – qualitative impairment of communication as indicated by at least one of the following:
      • Delay in or absence of spoken-language development.
      • Distinct impairment of ability to initiate or sustain conversations.
      • Repetitive and inflexible use of language.
      • Lack of spontaneous and varied “make believe” play.
    • Category three – repetitive stereotyped patterns of behavior, interests and activities indicated by one of the following:
      • Preoccupation with one or more inflexible and restricted activity patterns. These are abnormal either in intensity or focus.
      • Inflexible commitment to specific and nonfunctional routines and rituals.
      • Repetitive motor mannerisms, such as repeatedly rocking back and forth.
      • Preoccupation with parts of objects, such as focusing on the wheels of a bus.
  • Symptoms are not better explained by another PDD 

Asperger’s syndrome:

  • Symptoms are not better explained by another PDD or schizophrenia
  • Observable impairment in social interaction that includes at least two of the following:
    • Significant impairment in the use of multiple nonverbal gestures
    • Failing to develop relationships with friends
    • Lack of desire to share experiences with others
    • Lack of social or emotional reciprocity
  • Restricted repetitive and stereotyped patterns of behavior, interests and activities characterized by at least one of the following:
    • Intense preoccupation with one or more areas of interest
    • Rigid adherence to routines or rituals
    • Stereotyped and repetitive motor mannerisms
    • Preoccupation with parts of objects
  • Clinically significant impairment in social, occupational or other areas of functioning
  • Lack of clinically significant delay in language or cognitive development

Pervasive developmental disorder not otherwise specified:

  • Symptoms are not better explained by another PDD or schizophrenia, schizotypal personality disorder or avoidant personality disorder
  • Symptoms are not diagnosed as autism because:
    • They began later than indicated for autism
    • There are not enough present for diagnosis of autism
    • They are not typical of autism

Rett syndrome:

  • Normal development occurs prior to birth and for up to 5 months after birth, including normal head circumference at birth
  • The following losses occur:
    • Head circumference fails to properly develop between the ages of 5 and 48 months
    • Loss of hand skills between the ages of 5 and 30 months, which is replaced with repetitive movements such as hand-wringing
    • Loss of social engagement
    • Movement becomes uncoordinated
    • Severe language deficiencies occur

Childhood disintegrative disorder:

  • Normal development occurs for the first 2 years after birth
  • Losses occur (no later than 10 years of age) in at least two of the following areas:
    • Expressive or receptive language
    • Social skills
    • Bowel or bladder control
    • Play
    • Motor skills
  • Abnormalities occur in at least two of the following areas:
    • Social interaction
    • Communication
    • Restricted, repetitive behavior/interests
    • Symptoms are not better explained by another PDD or schizophrenia

Treatment options for PDDs

There is no cure for pervasive developmental disorders (PDDs). Symptoms and social difficulties faced by children with PDDs last a lifetime. These children may require lifelong care and supervision, depending on the severity of their disorder.

Therapy delivered to children with PDDs is designed to improve their communication and social skills, while reducing behaviors associated with PDDs. Efforts may also focus on educating parents on how best to elicit responses from children with PDDs.

Early intervention is important because it may have a dramatic effect on reducing a child’s symptoms, significantly improving their quality of life. Early intervention services (birth to 3 years old) provide developmental and supportive services through community agencies. The early childhood program (3 to 6 years old) assists in the transition to public school. School-based programs (to 21 years old) provide special education based on a child’s specific needs. As a child ages, this may include aiding in the transition to higher education (e.g., college), employment or independent living – depending on the severity of the child’s disorder.

Most therapies for children with PDDs should be highly structured. The objective is often to maximize communication. A team of professionals may be necessary to implement these therapies, and implementation can take place in the home, classroom and community. Some methods may be more effective than others, depending on a child’s particular strengths and weaknesses. Parents should consult with their child’s pediatrician to develop the treatment plan most appropriate for their child. These methods may include:

  • Behavior therapy. A type of learning therapy that attempts to eliminate inappropriate behavior by rewarding appropriate behaviors.
  • Relationship-focused therapy. Involves intense, scheduled play sessions between children with PDDs and their parents to increase a child’s responsiveness.
  • Speech and language therapy. Designed to teach children with PDDs to use language in a practical and meaningful way.
  • Physical therapy. Designed to develop muscle strength, coordination and gross motor skills. Desired physical movement may be obtained through various exercises.
  • Occupational therapy. Focuses on improving fine motor skills (e.g., brushing teeth, writing, eating) or sensory motor skills (e.g., balance). Sensory integration therapy may be used to reduce hypersensitivity to touch or sound through incremental exposure to stimuli.
  • Medication. In 2006, the Food and Drug Administration (FDA) approved the antipsychotic drug risperidone to treat certain behaviors associated with PDDs (e.g., irritability, aggression, self-injury, temper tantrums) in children and adolescents.

The large rise in the number of PDD cases has produced an equally large increase in available therapies purporting to treat the disorders. Many therapies have been studied and have been shown to have no proven value. Parents should discuss any therapy with their child’s medical team.

Some parents of children with PDDs have engaged in various complementary therapies to help their children. Dietary changes that eliminate gluten and casein (the main protein in milk) are advocated by some, although they have not been adequately studied. Other complementary therapies include art and music therapy, and animal therapy (e.g., horseback riding). Parents should consult their child’s pediatrician before adding any type of therapy to a child’s treatment plan.

Parents may wish to do the following at home to help children with PDDs:

  • Provide a structured home environment
  • Deliver consistent messages
  • Build routines
  • Provide love and support
  • Deliver verbal praise
  • Deliver rewards that stimulate social interaction (e.g., a trip to the park)

There is no known method of preventing PDDs.

Coping with pervasive developmental disorders

Pervasive developmental disorders (PDDs) can be especially devastating for parents.

Children with PDDs often appear cold and aloof, and parents can be emotionally hurt by the apparent indifference of their child. However, it is important to remember that these children experience emotion and feel affection, but are unable to communicate their feelings in the normal ways. Still, this lack of communication can be frustrating.

Parents may grieve the loss of behavior typically expected during childhood (e.g., cuddling). They may be embarrassed to take a difficult child out in public. Children with PDDs, too, may be frustrated at their inability to make their desires known. Thus, they may resort to screaming or grabbing when they want something, which can be incredibly stressful for caretakers.

The household changes required when caring for a child with a PDD can be emotionally draining and physically exhausting. Concerns about finances and future care can add stress to an already overburdened family. All of this can negatively impact a marriage, as well.

Some methods to help parents cope with a child with a PDD include:

  • Join a support group. This may provide much needed information and emotional support. It can let parents know they are not alone.
  • Take time out. This is extremely important to avoid caregiving burnout. The amount of time taken is not as important as the quality of time – even minutes can help.
  • Apply for financial aid. There are many different resources (e.g., federal and state agencies) available that may provide benefits to families caring for children with PDDs. Even a little financial help may help reduce the stress and cost of providing long-term care for a child with a PDD.
  • Attend counseling. This may include family, individual or marital counseling. Sharing feelings can prevent a person from feeling overwhelmed.
  • Other methods to reduce stress. This includes exercise, relaxation (e.g., deep breathing, meditation), prayer and journaling.

Ongoing research regarding PDDs

Research continues into identifying the specific genes responsible for pervasive developmental disorders (PDDs). Once these genes are revealed, scientists will begin the work of unraveling how these genes are triggered. They will also try to learn about how these genes affect certain areas of the brain and how these genes affect behavior.

In addition, the National Institute of Mental Health (NIMH) has launched three major clinical studies on autism and related disorders. One study will define differences, both biological and behavioral, in children who have autism with diverse developmental histories. Researchers also will investigate environmental factors that may trigger symptoms of autism in these children.

In another study, NIMH researchers will examine the use of the antibiotic minocycline to measure its usefulness in treating PDDs. Previous studies suggest that autism and associated disorders may be linked with changes in the immune system’sresponse that cause inflammation in the brain. Minocycline has known anti-inflammatory effects and has been found helpful in other neurological disorders such as Huntington’s disease.

The NIMH’s third study aims to test the efficacy and safety of chelation therapy for children with PDDs. Chelation treatment removes heavy metals from the blood and is commonly used to treat lead toxicity. Despite findings by the CDCthat indicate there is no connection between autism and related disorders with childhood vaccinations or with vaccines containing the mercury-based preservative thimerosal, some families continue to turn to chelation therapy to try to remove mercury and other metals from their autistic children’s blood.

Questions for your doctor regarding PDDs

Preparing questions in advance can help patients and parents have more meaningful discussions with physicians regarding their or their child’s treatment options. The following questions related to pervasive developmental disorders (PDDs) may be helpful:

  1. My child appears disinterested in social interaction and speech. Might he/she have a PDD?
  2. How can I tell the difference between a PDD and a child who is naturally shy and withdrawn?
  3. What type of PDD does my child have?
  4. What kind of tests will you have to perform to diagnose my child? How do we prepare for these tests?
  5. Will we need to see one or more specialists?  What kinds of physicians are these?
  6. What type of treatment will my child need for his/her PDD?
  7. My child has been diagnosed with autism. What are the chances future children of mine will have a PDD?
  8. Did my child’s vaccinations cause his/her disorder?
  9. Is my child eligible for financial aid services?
  10. Are there state agencies or local support groups you recommend we contact for financial, educational and emotional assistance?
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